Diesel emissions control system and method

ABSTRACT

The invention is embodied in a diesel system for reducing particulate matter emissions in off-road vehicles, coal mining and metal/non-metal mining operations, comprising, in combination, a supply of highly paraffinic diesel fuel having a high Cetane rating and substantially no sulfur, aromatics and nitrogen content and being formulated to greatly reduce PM output levels from the engine relative to conventional diesel fuels, The invention is further embodied in the method of reducing diesel emission contaminants including providing a supply of highly paraffinic diesel fuel having a negligible sulfur, aromatics or nitrogen content, and a high Cetane number, and other apparatus useful for filtering engine emissions before discharge to ambient.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part of U.S. application Ser. No. 11/194,371 filed Aug. 1, 2005 which was a continuation-in-part of application Ser. No. 11/074,595 filed Mar. 8, 2005, the entire disclosures of both earlier applications being incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to diesel fuel systems, and more particularly to diesel systems and methods for substantially reducing hydrocarbon and diesel particulate matter levels in diesel exhaust emissions to safe environmental levels particularly in underground mining.

2. Description of the Prior Art

Internal combustion engines are designed to operate most efficiently on standard quality fuels, and the presence of impurities or non-combustible contaminates may result in poor engine performance or impairment as well as produce higher levels of exhaust impurities. Even small quantities of water in diesel fuel may prevent satisfactory operation of a diesel engine, and most diesel engines now have some type of water-separator in addition to filters for removing sediment or other solids that may have been introduced into the fuel tank. It is also now known that the presence of air entrained in diesel fuel delivered to a fuel injection system results in poorer engine performance since the amount of air required for optimum combustion is already precisely controlled by the fuel injection system itself. In addition, the sulfur content in petroleum-based diesel fuels, including No. 2 diesel products, is one of the major reasons the fuel injectors catalytic converters fail. It is thus clear that the presence of these non-fuel contaminates in a diesel fuel delivery system result in poor engine performance with the extended result of less complete fuel burning and an increase in deleterious exhaust pollutants.

During operation even state-of-the-art diesel engines using conventional petroleum-based and so-called low sulfur (No. 2) diesel fuels produce various exhaust pollutants including unburned hydrocarbons, carbon and nitrogen oxides, sulfurous gases and other particulate matter generally called “diesel particulate matter” (DPM) or just “particulate matter” (PM). Aside from the environmental interests and governmental regulations for reducing such air pollution generally, there is an absolute necessity of doing so in certain diesel operating environments. There is a prevalent use of diesel engine powered equipment in fiery gaseous mining applications where methane gas is present; and the Federal government, through the Mine Safety Health Administration (MSHA), has set rigid regulations for the design and operation of all classes of diesel engines operating underground mining machinery.

The control of exhaust gas emissions has been a primary troublesome concern for health and safety reasons, and the Federal government has heretofore mandated the use of “soot trap filters” to reduce DPM emissions levels by filtering hydrocarbons out of the diesel exhaust gases. However, the use of dry filter soot traps on the end of a diesel exhaust has generally posed a fire hazard problem irrespective of what the filter material (steel, fibreglass, ceramic, etc.) is made of, since any buildup of DPM hydrocarbons at normal engine and exhaust operating temperatures may cause an explosion in a gaseous coal mine. For instance, diesel engine combustion temperatures may be 800°-1100° F., so significant engine and exhaust pipe cooling should be effected to reduce gas emissions temperatures below the ignition temperature of hydrocarbon accumulations in the soot trap. High exhaust gas temperatures are especially hazardous in the operation of class 32 diesel engines in coal mines or like closed environments where methane gas may be present. Methane has an ignition temperature of 302° F. and, in past practice, the exhaust lines from class 32 diesel engines have been insulated with “Thermogram” or the like so that the high (800° F.) combustion temperature of diesel exhaust gases would be carried to the soot trap thus producing the probability of fires and/or explosions therein. The result is that many mine operators refuse to use the mandated soot traps for safety reasons and generally continue to operate under violation citations from the Mine Safety and Health Administration (MSHA), which has promulgated a low—and heretofore unachievable-DPM emissions level of 2.5 gr/bhp-hr.

It has been reported that dry soot traps are still fire hazards even after the engine is shut off because oxygen will flow from ambient back into the hot trap and ignite the carbon/hydrocarbon DPM accumulation therein. In short, any dry soot trap per se almost always poses a fire hazard and, in addition, soot traps are labor intensive and expensive.

In the past the foregoing fire hazard problem has been approached by attempting to provide exhaust gas cooling means, generally in the form of a so-called gas scrubber consisting of a body of water into which the exhaust gases were passed and cooled. Typical prior art water scrubbers are the following U.S. patents: U.S. Pat. No. 3,957,467 granted May 18, 1976 (Kim); U.S. Pat. No. 3,976,456 granted Aug. 24, 1976 (Alcock); and U.S. Pat. No. 4,190,629 granted Feb. 26, 1980 (Strachan). However, the apparatus of these patents primarily only cools the exhaust gas, but has no other major effect since only a small portion of DPM matter will be trapped in plain hard mine water, and also no significant carbon monoxide or sulfur will be removed. The Kim patent U.S. Pat. No. 3,957,467 states that a gas purification liquid may be used and, in addition to water alone, it is suggested that aqueous solutions may have additives such as detergent, surfactant or wetting agents, alcohol, glycol or alkalis, but no specific example or function is taught.

In addition to the rigid regulations set by MSHA for diesel equipment operating in fiery gaseous underground mining operations there is another class of underground mining referred to as “metal/non-metal” such as ore mining and hard rock tunneling and construction in general. Diesel equipment in such closed operations may be subject to regulation by the MSHA because of the environmental health hazards caused by particulate matter (PM) emissions therein.

SUMMARY OF THE INVENTION

The invention is embodied in systems for reducing diesel particulate matter (DPM) in diesel engine emissions by providing a high paraffinic diesel fuel having a Cetane rating greater than 60 and substantially no sulfur, aromatics or nitrogen content, and using such fuel alone or in combination with filtration means comprising an aqueous filter apparatus forming a water bath having a major water portion and a minor portion of super-wetting agent with a high affinity for hydrocarbons. The invention is further embodied in a diesel emissions control methods including the features of high paraffinic diesel fuel selection, pre-filtering diesel fuel, and removing DPM from diesel emissions through an aqueous solution having a minor portion of a low foam super-wetting agent.

A principal object of the invention is to provide systems, apparatus and methods for removing significant amounts of diesel particulate matter (DPM) from diesel engine gas emissions prior to final discharge thereof to ambient in coal mining operations.

Another object is to substantially reduce carbon monoxide levels in the final emission gases prior to discharge to ambient in all types of mining.

Another object is to provide synthetic paraffinic diesel fuels to thereby achieve substantial reductions in particulate emissions from the engine.

Still another object is to provide a synthetic high paraffinic diesel fuel formulated to produce substantially lower particulate emissions from diesel engines, and also being useful alone or in combination with pre-filtration to remove non-combustible matter upstream of the engine and DPM filtration of emission gases downstream of the engine to thereby comply with the Federal Regulation levels prescribed for underground diesel.

An object of the invention is to provide a diesel filtering method comprising pre-filtering diesel fuel to remove non-combustible matter upstream of the engine, and removing DPM and carbon monoxide from diesel exhaust gases downstream of the engine, and final filtering the exhaust gases before discharge to ambient.

Another object of the invention is to provide more effective ways of removing DPM and carbon monoxide matter from diesel exhaust gases using economically priced synthetic fuels and low cost filtration systems and equipment and labor saving methods.

It is another objective to greatly improve the working environment around diesel powered equipment in all types of mining, especially in metal/non-metal mines.

It is another objective to greatly improve the working environment around diesel powered equipment, particularly in coal mines and like underground sites with potential methane gas or other hazardous gas presence.

Another object is to provide a linear paraffinic-type synthetic diesel fuel for use with exhaust gas scrubber systems and methods that together are effective in removing DPM matter and carbon monoxide from diesel emissions prior to passing to any final filter mandated by MSHA, and which will thereby prolong the useable life and reduce the costs of using such final filters. It is a still further object to provide such fuels, systems, apparatus and methods whereby the present requirements for final exhaust filters may be ameliorated.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings wherein like numerals refer to like parts wherever they occur:

FIG. 1A is a diagrammatic view showing a diesel fuel system embodying one aspect of the invention from fuel tank to emissions exhaust;

FIG. 1B is a more detailed diagram of the diesel fuel system embodiment of Figure A;

FIG. 2A is a diagrammatic view showing another aspect of the invention;

FIG. 2B is a more detailed diagram of the FIG. 2A embodiment;

FIG. 3 is an enlarged cross-sectional view of the emissions exhaust filtering section of the FIG. 1A system;

FIG. 4 is an enlarged cross-sectional view of another embodiment of the exhaust filtering section of the FIG. 1A system;

FIG. 5 is a sectional plan view taken along line 5-5 of FIG. 4;

FIG. 6 is a diagrammatic view illustrating another embodiment of an emissions exhaust filtering section of the invention;

FIG. 7 is another diagrammatic view showing a further embodiment of the exhaust filtering section; and

FIG. 8 is a cross-sectional view taken along line 8-8 of FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Emission control systems of the prior invention will be more clearly understood with reference to the following definitions. DEFINITIONS:

“Synthetic Fuel” is used herein as a generic term identifying a class of diesel engine fuels that encompasses synthetic fuel blends and specified solvent fuels. Synthetic fuels are produced by processes, such as Fischer-Tropsch (F-T), for converting gas-to-liquid (GTL) or coal-to-liquid (CTL). The synthetic fuels of this invention are further characterized by a high Cetane number, and low sulfur(S), aromatics (A) and nitrogen (N) constituents resulting in a clean burning fuel having low PM emissions.

“Synthetic fuel blends” is used to identify a form of synthetic diesel fuel having a preponderance of synthesized components combined with a minor portion of a petroleum-derived constituent.

“Solvent fuels” is used herein to identify a group of products synthesized by F-T processes or the like and having the characteristics of synthetic fuel and can substitute therefor as low PM emission fuels.

“Fischer-Tropsch” also called “F-T” is used generically herein to identify chemical processes for the conversion of natural gas into liquid fuel (the GTL process) or the conversion of coal into liquid fuel (the CTL process).

“Off highway” (or “off road”) as used herein shall mean any diesel equipment not registered for or meeting emissions and vehicular standards for highway and street operation

“Non-road” as used herein shall encompass off highway diesel equipment and more specifically apply to mobile vehicles and equipment in the following categories:

airport ground support

agricultural equipment

construction equipment

forestry and logging equipment

industrial and commercial equipment

recreational off road vehicles

recreational marine vessels

residential and commercial lawn and garden equipment

underground mining and oil field equipment

“Coal mine” or “coal mining” is used herein as a comprehensive term that includes any fiery gaseous underground mining operation wherever class 32 and/or class 24 diesel equipment/machinery is designated.

“Metal/non-metal mine” or “metal/non-metal mining” is used herein as a generic or comprehensive term to mean any type of underground mining that does not have a fiery gaseous environment requiring diesel equipment/machinery in compliance with class 32 or class 24 MSHA regulations, such as ore mining and hard rock construction operations.

Referring to the diagrammatic overview of a diesel fuel system of the invention as shown in FIGS. 1A and 1B, this system includes a fuel delivery section FD including tank 10 and an emissions exhaust section EE between the diesel engine 12 and ambient.

The fuel tank 10 of the fuel delivery section FD according to the present invention provides a supply of synthetic fuel formulated to result in engine exhaust emissions having a reduced particulate matter content of about 20%-40% relative to conventional petroleum diesel fuels, inclusive of No. 2 or like so-called low sulfur diesels. Such performance pre-supposes the use of a electronic state-of-the-art diesel engine, such as a Deutz 1013C engine, appropriately derated for the atmospheric levels of operation. It should also be noted at the outset that the present invention is particularly beneficial for diesel machinery operating in underground mines of all types especially wherein expensive additional equipment and/or increased labor may have heretofore been required such as to remove particulate soot traps for regeneration (cleaning) outside the mine.

Synthetic diesel fuels of the present invention are primarily identified as linear paraffinic types of synthetic hydrocarbon solvents or diesel fuels with properties that meet the standards prescribed for compression ignition engines. Such synthetic fuels are within a range of linear paraffin and isoparaffin hydrocarbons alone or in combinations with cycloparaffins (naphthenic paraffins), and sometimes called linear paraffinic-linear olefinic diesels. The synthetic fuels may include a small part of a petroleum based product for lubricity.

The synthetic diesel fuel of the invention has substantially no sulfur, nitrogen or aromatics, i.e., less than 1.0%. It has a high Cetane number above 60, in the range of about 60 to 100 and preferably in the range of about 65 to 80. In one example, the synthetic diesel fuel is a high purity mixture of hydrotreated isoparaffins, naphthenics and linear saturated paraffins with low or negligible levels of aromatics, sulfur and nitrogen (less than 1.0% each) and has a Cetane number of 75. This synthetic diesel fuel is designated as UGD-S200 and is available from Brady's Mining and Construction Supply Co. (St. Louis, Mo.) and from Lancer Industries (Dallas, Tex.).

In another example, synthetic diesel fuel designated as UGD grade 175 is a high purity mixture of about 75% linear paraffins and 13% linear olefins with less than 12% of branch paraffin/olefins and it has a Cetane number less than 70. Its sulfur content is less than 1.0%, its nitrogen content is less than 1.0% and its aromatics content is less than 0.5%.

A third example designated as UGD Grade 70 is available from Lancer Industries (Dallas, Tex.) and Brady's Mining and Construction Supply Co. (St. Louis, Mo.). It has a Cetane number of 68 and has 0.0001 sulfur content and 0.5 aromatics (by Cetane Index).

Another feature of the invention is to deliver a substantially pure supply of the synthetic diesel fuel to the engine, i.e., fuel that is substantially free from air, water and other unwanted gases or non-combustible contaminates. Thus, with reference to FIG. 2 in the preferred embodiment, the fuel delivery section FD of the diesel system includes a source of pure highly paraffinic fuel 10, fuel pre-filtration means including a water filtration or separator unit 14 connected by fuel line 15 to the fuel tank 10, and a particle filtration unit 18 connected in line 17 through fuel pump 20 to the water filter 14. In this preferred embodiment the water filter unit 14 and particle filter unit 18 form a primary or initial fuel filter means 21, and a secondary fuel filter means 22 is connected through a flow rate regulator valve 24 in line 23 to the primary filtration means 14, 18.

The secondary fuel filter 22 includes a vessel 26 having an interior separation chamber 27 constructed and arranged to fluidically connect through delivery line 28 to the electronic fuel injection system (not shown) for the engine 12, and also has a return line 29 connecting back to the fuel tank 10. An air purge means (not shown) can be provided at the top of the vessel 26 to bleed air out of the fuel delivery system. U.S. Pat. Nos. 5,746,184 and 5,355,860 are incorporated by reference as disclosing features of one suitable pre-filtration means of the fuel delivery section FD in greater detail.

In operation, the fuel delivery section FD provides for the positive delivery of diesel fuel from the fuel tank 10 to the injection system (not shown) of diesel engine 12. Pump 20 assures positive flow through both the primary and secondary fuel filter means 21, 22 in which air, water and other non-fuel impurities are removed. Thus, optimum engine performance can be achieved through pre-filtration of diesel fuels with the result that maximum burning of diesel fuel will result in lower levels of diesel particulate matter (DPM) in the emission exhaust gases from the engine 12. As stated, with the use of linear paraffinic-type diesel fuels of this invention, potential DPM emission levels can be reduced by as much as 40% in the engine 12. It should also be noted that some characteristics of the present synthetic diesel fuel are the substantial absence of any sulfur, aromatics and nitrogen content (less than 1%). Accordingly, it is now recognized that the use of certain selected synthetic diesel fuels to power diesel equipment in various mining operations such as metal/non-metal mines will result in a substantial reduction in PM emissions, thereby improving environmental conditions and meeting MSHA objectives. Nonetheless, for the most part the unburned hydrocarbon or PM content of engine emission gases, as in the past, may continue to be a major safety and health concern in the operation of diesel engines in many environments—particularly in closed, poorly ventilated areas such as underground mines.

Another major feature of the invention is to deliver diesel engine discharge gases (with inherent hydrocarbon DPM content) through the emission exhaust section EE, which includes exhaust gas scrubber means for safely removing such DPM content, reducing carbon monoxide levels and discharging cleaned exhaust gases to ambient. The effectiveness of this feature of the invention is achieved primarily by providing an aqueous solution in the gas scrubber section EE that includes a super-wetting agent (“wetting composition”).

Referring to FIGS. 1A, 1B and 3 of the drawings, the exhaust scrubber portion EE of the system includes an aqueous filter apparatus positioned in the exhaust output passageway from the diesel engine 12 to ambient. More specifically, the aqueous filter apparatus forms a water bath WB through which all DPM laden emission gases are passed and cleaned before being discharged to ambient. In a preferred form of the invention, the water bath WB of filtering apparatus is contained in a scrubber tank 33 that has an exhaust intake 34 connected by exhaust pipe 35 to the exhaust manifold (not shown) of the engine 12. The exhaust pipe 35 is covered by a suitable insulation covering 36, such as “Thermogram”, to shield the high discharge gas temperatures (i.e., 800° to 1100° F.) from the surrounding ambient. In FIG. 3 it will be seen that the tank 33 has an internal extension pipe 37 connected to the exhaust pipe 35 and extending into the tank 33 below the level 38 of the water bath WB. A gas discharge diffuser 39 is provided at the exit end of the exhaust extension pipe 37 to break up and disperse the exhaust gas stream as it is discharged from the extension 37 into the water bath WB in the tank 33. For illustration purposes the diffuser 39 is simply shown as an elongate pipe having a series of discharge openings 40, but it will be understood that a wide variety of gas diffusing means, such as in the form of perforations, screens and turbulence producing means, may be employed. The openings 40 are preferably arranged along the length and around the circumference of the diffuser 39. The diffuser means (39) of the invention should act to disperse or spread out the gas stream for mixture into or percolation through the water bath WB and it may act to partially decelerate the entering gas stream to a lower velocity.

It is important that any retardant effect of exhaust gas dispersion should be controlled to a minimum so as to not create undue backpressure on the diesel engine 12. Recent MSHA regulations have set 34 inches of mercury as a backpressure maximum for off road diesel applications. Thus, the size and exhaust discharge rate of the diesel engine and the water bath capacity of the scrubber tank are important factors in designing an emissions flow path that will meet this requirement. For instance, sizes of diesel engines for underground mining equipment (or off-road machinery in general) vary widely—from a 90 Hp 4-cylinder Deutz engine having a 340 cfm output to a 150 Hp 6-cylinder Deutz engine with a 1275 cfm output. An inclusive range of up to 1500 to 2000 cfm must be accommodated and correlated to water bath capacity in the scrubber tank. Thus, the 1275 cfm exhaust output of the 6-cylinder engine will require a water bath capacity of about 84 gal. to absorb about 30% or more of the DPM from the emission gases. Therefore, the water bath capacity may vary between 20 to 90 gal. to accommodate different sizes of diesel-engines and meet the DPM removal requirements from exhaust gases. The scrubber tank 33 may be any suitable shape, such as cubicle or cylindrical, and constructed to hold the predetermined volume of 20 to 90 gallons.

The exhaust intake 34 is located at one end of the tank 33, and the tank also has a gas discharge or outlet 42 located at the other tank end and positioned above the water bath level 38 in such manner that the exhaust gases must traverse through the water bath the length of the scrubber tank 33 from the diffuser (40) at the intake end to the outlet port 42 at the exit end. A final filter 43 of ceramic or fiberglass is shown connected at the gas discharge outlet (as currently mandated by MSHA for class 32 diesel operations). It is believed that the present invention will minimize any need for a final filter 43, as will be shown.

In addition to the diffusing means (39, 40) for dispersing or breaking up the exhaust gas stream as it enters the water bath WB, the tank 34 is provided with baffle means (44, 45) projecting vertically into the body of water in the tank and extending across the tank from side to side. The baffle means (44, 45) are constructed and arranged to create tortuous or circuitous gasflow pathways to increase the turbulence and mixing contact of DPM laden gas molecules with the water bath WB. In the form of the invention shown in FIG. 3, first baffles 44 are arranged to extend upwardly from the floor 46 of the tank or just above the floor, and have upper ends 44 a below the water level 38. Second baffles 45 are arranged to extend downwardly from the top 47 of the tank and have lower end margins 45 a within the water bath and spaced above the floor 46. The first and second baffle means are alternately arranged to create major tortuous pathways having primary vertical channels there between and being connected around the baffle end margins (44 a, 45 a), as shown by the curved arrows. The baffles 44, 45 are also shown with minor secondary through-ports 49 to provide for small portions of exhaust gases to flow directly through these baffles and impinge on the major gas portions flowing in a vertical direction in the primary vertical passageways whereby to cause further turbulence and scrubbing action between the gases and the water bath WB. It should be noted that an imperforate section of the baffles 45 extend across the tank from the top (47) downwardly into the water bath thereby forming a vapor barrier or seal above the waterline so that exhaust gases must flow through the water bath in the major passageways to reach the final exit port 42 from the tank 33. The tank 33 also has a water fill pipe 50 and water level float 51, and the bottom of the tank may have an outlet 74 or like drain provision for periodic flushing of the tank as may be required. Because of the MSHA regulation limiting exhaust gas backpressure to about 34 inches mercury, it may be necessary to limit the number of baffles to two—one upward baffle 44 and one downward baffle 45. In the FIG. 1B embodiment in which the tank 33 may hold a water bath depth of about 12 to 14 inches, the two baffles (44, 45) would result in an exhaust gas flow path of about 28 to 34 inches. Thus other dispersion means for exhaust gases in the tank have been found beneficial and will accommodate a water bath depth up to 18 to 20 inches mercury.

Referring now to FIGS. 4 and 5, in another embodiment of the invention the vertical baffles (44, 45) of FIGS. 2 and 3 may be eliminated. In FIGS. 4 and 5, the scrubber tank has an exhaust intake 334 connected by exhaust pipe 335 to the exhaust manifold (not shown) of the engine 12 and being covered by “Thermogram” insulation 336 or the like. The tank has an internal extension pipe 337 of larger size connected to the exhaust pipe 335 and extending below the level 338 of the water bath WB. Gas discharge diffuser means 339 are provided at the exit end of the exhaust extension pipe 337 to break up and disperse the emission gases discharged into the water bath WB. For illustration purposes, in this embodiment the diffuser 339 is bifurcated to form a pair of parallel elongate pipes 339 a and 339 b extending near the bottom 346 of the tank 333. These discharge pipes 339 may be round or flat or are otherwise constructed and arranged to enlarge the volume capacity of the diffuser (339) to reduce flow resistance at the point of gas discharge downwardly and outwardly through a series of ports 340 into the water bath WB. It will be understood that a wide variety of gas diffusing means may be employed. The openings 40 are preferably arranged along the bottom and lower sides around the diffuser 339. The diffuser means (39) of the invention should act to disperse or spread out the gas stream for mixture into or percolation through the water bath WB. In addition, it may be desirable and even beneficial to provide an optional horizontal baffle plate 341 across the tank 33 above the diffuser branches 339 a and 339 b to thereby increase the percolation effect through holes 341 a and provide a more turbulent intermixture of the emission gases in the super-wetting solution.

Due to the high velocity of exhaust gases flow into the water bath and the desire to obtain optimum intermixture as surface contact there between, the internal extension pipe 337 may be twice the size of the exhaust pipe 335 and open into diffuser pipes 339 a and 339 b that also double the delivery capacity for exhaust gases. Thus an added feature of the invention is to enhance the circulation and intermixture of the water bath liquid with the incoming exhaust gas flow by providing an aspirator inlet opening 337A in the extension pipe 337 below the water level 338 of the water bath WB. A simple port 337A is shown whereby a venturi affect will be created and the water bath will be aspirated into the downward gas stream and thoroughly intermixed therewith before being discharged out into the bottom of the tank 333. A Y-connection (not shown) or T-joint (not shown) may be used to function as a feed tube for the water bath solution to be drawn into the extension pipe (at 327A). Thus, a circulating current of liquid is created at the gas inlet end of the tank, and the further turbulent gas/liquid discharge outwardly through diffuser ports 340 (and upwardly through the baffle plate ports 341 a) will assure excellent mixing and DPM removal by the super-wetting solution. It will be readily apparent that a liquid aspirating inlet (337A) may be provided in other embodiments of the invention. Any retardant effect on gas flow through this water bath should be minimized to reduce undue backpressure on the diesel engine 12.

Referring now to FIGS. 2A and 2B, it will be seen that synthetic diesel fuels of the present invention may be used in systems not requiring any final hydrocarbon clean-up or other PM filtration of emission gases. Thus, the exhaust 435 from diesel equipment operating in metal/non-metal mining may be connected to a catalytic converter CC having a casing 488 with sound absorbing materials 490 and/or baffle members 491 constructed and arranged interiorly to provide circuitous exhaust gas flow paths as well as muffle diesel engine 412 operating noises. It will be apparent that the metal/non-metal mining of ores and rock do usually not involve gaseous atmospheres where the PM/DPM problems with potentially explosive hydrocarbon build-up may exist.

The following further definitions will be instructive in the further disclosure and claiming of the invention: “DPM” (diesel particulate matter) as used herein shall generally mean all forms of hydrocarbon and other carbonaceous matter, carbon or nitrogen oxides, sulfurous gases and related particulate matter. DPM may also be referred to as “particulate carbonaceous matter”.

“Super-wetting agent” or wetting solution as used herein shall generally mean an aqueous mixture comprising a combination of a chemical hydrocarbon cleaner and a defoaming agent, the composition typically in the form of a colloid, suspension, emulsion or solution.

A “colloid” (i.e., colloidal system) as used herein shall generally mean a dispersion of finely divided particles in a continuous liquid medium—the particles being in a mid-size range between a true solution (1 millimicron or nanometer) and a coarse dispersion or suspension (1 micron or micrometer).

“Emulsion” as used herein shall generally mean a stable mixture of two or more immiscible liquids held in suspension by a surface-active “emulsifier” that is either (1) a protein or carbohydrate polymer which coats the surfaces of dispersed fat (oil) particles to prevent coalescing (called a protective colloid) or (2) a long-chain alcohol and fatty acid which reduces surface tension at the interface of suspended soluble particles. Emulsions consist of a continuous phase and a disperse phase in which small globules of one liquid are suspended in a second liquid by a wetting or deterging agent.

“Detergent” as used herein generally means any deterging or cleaning agent produced from synthetic organic compounds (rather than natural fats or oils and alkali as in soaps). Detergents are soluble in water, and highly foamable and act as a wetting agent and emulsifier.

“Soap” as used herein shall generally mean a deterging or cleaning agent made by reacting a natural fatty acid (e.g., tall oil fatty acid) or oil with an alkali or caustic (such as sodium or potassium hydroxide or an alkanolamine such as monoethanolamine) to produce the corresponding soap with glycerol as a by-product. Soaps, like detergents, exhibit surface-active properties, such as foaming, detergency and lowering of surface tension.

“Surfactant” as used herein shall mean any of the class of surface-active agents including (or are included in) detergents, soaps, colloids and emulsifiers. Surfactants are surface-active agents that reduce the surface tension of water and cause it (1) to penetrate more easily into, or spread over the surface of, another material or (2) be penetrated by or become a dispersion of another material. Surfactants are wetting agents that orient themselves at the molecular interface of water with other surfaces and modify the liquid properties at the interface. A surfactant typically consists of two parts: a hydrophobic portion (e.g., a long hydrocarbon chain) and a hydrophilic portion that makes the entire compound soluble or dispensable or dispersable in water and these hydrophobic and hydrophilic moieties render the compound surface-active. Surfactants suitable for use in the practice of the present invention are generally classified as anionic, cationic, nonionic, or amphoteric.

An important aspect of the invention resides in the selection of a suitable combination of chemical hydrocarbon cleaner and defoaming agent to formulate an acceptable wetting solution composition for use in the aqueous mixture of the water bath WB. In the past, water scrubbers have been placed in diesel exhaust lines to cool exhaust gases and, of course, some amount of particulate soot matter may become suspended in the water. However, it is known that the carbonaceous matter or DPM is basically immiscible in water and that only a very small portion of DPM will actually be removed in these prior art traps; and that no carbon monoxide will be removed therein. Thus, it is presently mandated that all scrubbers (soot traps) of any kind used on underground class 32 and/or class 24 outby diesel equipment in coal mines be equipped with a “stop work float device” to ensure that hydrocarbon sludge accumulation does not reach kindling temperature and catch fire. It is also known that various natural and chemical surfactants, detergents and/or wetting agents in aqueous solution can attract hydrocarbons from exhaust gases and hold a limited amount of them in the water of a scrubber, but the resulting foaming action of such additives often creates other unacceptable conditions and environmental problems.

It will be understood that the wetting composition of the invention should preferably be able to function effectively in hot environments (e.g., about 800° to 1100° F.), which is the typical temperature range of exhaust gases entering the aqueous solution of the scrubber (33). Furthermore, the wetting composition should desirably be able to react very fast and bond with hydrocarbons and carbon compounds and pull them from the exhaust gases. It is believed that the high gas temperature may act to accelerate this bonding reaction of the chemical hydrocarbon cleaner (e.g., surfactant) with the DPM and also the removal of carbon monoxide (CO) from the exhaust stream. The turbulence generated by the rapid flowing exhaust gases entering the scrubber and being dispersed by the diffuser through the water bath produces greater surface area contact and more complete removal of DPM and CO from the exhaust.

The chemical hydrocarbon cleaner is preferably selected so as to be able to substantially reduce the amount of DPM and CO present in the exhaust gas entering the scrubber. In addition, a suitable wetting composition should have a fast reaction time in attracting and holding DPM due to the high velocity of the exhaust gas stream entering the scrubber tank (33), even though the diffuser means (39) may have some flow retardant effect on the dispersed gas. In one embodiment, the present invention scrubber attracts and holds the DPM at least 3 to 5 times faster than previous scrubbing methods.

In accordance with one aspect of the present invention, suitable wetting compositions have been formulated for use in conjunction with a diffusing means for dispersing exhaust gases throughout the water bath of a scrubber, thereby obviating prior art shortcomings and achieving superior diesel exhaust gas cleansing of DPM and reduction of carbon monoxide levels.

The chemical hydrocarbon cleaner may be suitably selected from various detergents, soaps, surfactants and mixtures thereof. Preferably, in order to alleviate environmental concerns, the super-wetting composition is formulated to be phosphate and nitrate-free. In addition, the chemical hydrocarbon cleaner is low-foaming to mitigate production of foam during use. Nonionic surfactants generally have lower sudsing or foaming characteristic than anionic surfactants, and the chemical hydrocarbon cleaner utilized in the wetting composition preferably comprises a nonionic surfactant.

Examples of suitable nonionic surfactants for use in the chemical hydrocarbon cleaner component of the wetting composition include ethoxylated alcohols, alkanolamines, and mixtures thereof. In accordance with a preferred embodiment, the chemical hydrocarbon cleaner includes an ethoxylated nonylphenol nonionic surfactant, for example, n-molar ethoxylated nonylphenols or mixtures thereof, sometimes denoted as nonoxynol-n, where n is a rational number between about 2.5 and about 15. Such nonionic surfactants are available from Huntsman Chemical (Salt Lake City, Utah).

Even in embodiments where a low-foaming nonionic surfactant is employed as the hydrocarbon cleaning agent, the wetting composition of the present invention advantageously further includes an additional defoaming agent to provide a wetting composition that maintains a substantially liquid state at all times. The concentration of the defoaming agent in the wetting composition generally is at least about 1% by weight, more typically in the range of about 5% to 15% by weight. The defoaming agent is dispersable in the other components of the wetting composition.

Examples of suitable defoaming agents include petroleum-based antifoams (e.g., 2-octanol, sulfonated oils, organic phosphates) and silicone-based antifoams. However, it has been found that petroleum-based antifoams may be susceptible to degradation in the wetting compositions disclosed herein and may not provide the desired level of foam mitigation during use after prolonged periods (e.g., 1 to 2 days) following formulation. Accordingly, in such embodiments, the wetting compositions can be prepared for use in aqueous solution as a single or one part product; or the remainder of the composition can be packaged separately from the petroleum-based antifoam to be combined with the remainder of the composition just prior to use at the diesel operating site. In order to provide a super-wetting composition capable of sufficient foam mitigation and longer effective shelf-life, it is preferred that a silicone-based antifoam be utilized as the defoaming agent. Specific examples of silicone-based antifoams include silicone fluids and organosiloxanes. In accordance with an especially preferred embodiment, the defoaming agent comprises a polydimethylsiloxane available from General Electric (Waterford, N.Y.), such as those sold under the product designations AF900, AF9010, AF9020 and AF9030.

In one preferred embodiment wherein the chemical hydrocarbon cleaner component comprises a nonionic surfactant comprising an ethoxylated nonylphenol in combination with monoethanolamine or other alkanolamine, the wetting composition may advantageously be formulated with a tall oil fatty acid. In such an embodiment, the tall oil fatty acid is saponified at least to some extent with the alkanolamine caustic to form a soap.

The wetting composition of the present invention may include a variety of optional components in addition to the chemical hydrocarbon cleaner and the defoaming agent. For example, the composition, when a surfactant (e.g., a nonionic surfactant) is utilized as the chemical hydrocarbon cleaner may further include an organic solvent. In such embodiments, the organic solvent may provide composition thinning or fluidity in the form of a colloid. Suitable non-limiting examples of organic solvents include alkylene glycol ethers such as dipropylene glycol methyl ether.

One representative preferred aqueous wetting composition useful in treating diesel emission gases comprises a chemical hydrocarbon cleaner in the form of ethoxylated nonylphenol nonionic surfactant and a soap formed by saponifying a tall oil fatty acid with monoethanolamine; an organic solvent comprising dipropylene glycol methyl ether; a coupling agent comprising tetrasodium EDTA; and a defoaming agent comprising a silicone-based antifoam.

Another representative preferred wetting composition in accordance with the present invention comprises at least about 35% by weight water; a chemical hydrocarbon cleaner comprising an ethoxylated nonylphenol nonionic surfactant and a soap formed by saponifying a tall oil fatty acid with monoethanolamine, wherein the composition comprises from about 10% to about 30% by weight ethoxylated nonylphenol nonionic surfactant, from about 2% to about 8% by weight tall oil fatty acid and from about 1% to about 5% by weight monoethanolamine; an organic solvent comprising dipropylene glycol methyl ether, wherein the composition comprises from about 5% to about 15% by weight dipropylene glycol methyl ether; a coupling agent comprising tetrasodium EDTA, wherein the composition comprises at least about 0.5% by weight tetrasodium EDTA; and a defoaming agent comprising a silicon-based antifoam, wherein the composition comprises at least about 1% by weight silicon-based antifoam. Preferably, the ethoxylated nonylphenol nonionic surfactant comprises nonoxynol 10 and the silicone-based antifoam comprises a polydimethylsiloxane. Examples of wetting compositions in accordance with the present invention include products designated Aqua Filter Nos. 195D, 942D and 735D available from Brady's Mining and Construction Supply Co. (St. Louis, Mo.). These wetting compositions each have a multiple surfactant base of low foaming surfactants plus a silicone-based antifoam.

In formulating these preferred wetting compositions of the present invention it may be useful to start with the colloidal surfactant blend designated B/F100P, available from Foresight Chemical (Troy, Ill.) and Brady's Mining and Construction Supply Co. (St. Louis, Mo.). This product comprises a colloid containing nonoxynol 10, dipropylene glycol methyl ether, monoethanolamine, tall oil fatty acid and tetrasodium EDTA. Accordingly, B/F100P can be used as a suitable base for formulating the wetting composition described herein. In one embodiment, a suitable quantity of defoaming agent (e.g., polydimethylsiloxane) may be added to produce the wetting composition. However, in order to provide a more effective wetting composition having desirable fluidity characteristics, it is preferred to add additional quantities of nonoxynol 10 and tall oil fatty acid as necessary along with the defoaming agent to obtain the desired composition. Preferably the B/F100P base composition is heated to a temperature of from about 125° to about 175° F. during addition of these ingredients. Typically, additional dipropylene glycol methyl ether is added in order to thin the composition and ensure sufficient fluidity in the final wetting composition. For example, in one embodiment, a suitable wetting composition may be prepared by mixing approximately 70 parts by weight of B/F100P with approximately 30 parts by weight of a low foaming surfactant including approximately 10 parts by weight of a silicone-based defoaming agent.

Although a preferred wetting composition as described above includes an ethoxylated nonylphenol nonionic surfactant as the chemical hydrocarbon cleaner, those skilled in the art will be able to identify other surfactants, detergents, soaps and mixtures thereof for use in combination with a defoaming agent. Examples of such chemical hydrocarbon cleaners include the surfactants found in JOY brand dishwashing liquid (Procter and Gamble, Cincinnati, Ohio) and PALMOLIVE brand dishwashing liquid (Colgate-Palmolive, New York, N.Y.). Suitable anionic surfactants include alkylether sulfates, alkyl sulfates and mixtures thereof.

From the foregoing, it will now be apparent that the selection and use of linear paraffinic-type synthetic diesel fuels alone or in combination with an emission gas scrubber produces remarkable results in clean-emission performance of underground diesel equipment in both metal/non-metal and coal mining operations. The particulate toxins normally found in diesel fuels and diesel emissions can be reduced by 20% to 40% at the engine performance level alone, and the DPM level of emission gases can be further reduced by an additional 80% in the exhaust scrubber EE for a total reduction of 88%. In addition, up to about 99% of DPM can be removed when the water bath scrubber (33) is used in conjunction with a final filter (43).

The synthetic diesel fuel of the invention has substantially no sulfur, nitrogen or aromatics, i.e., less than 1.0% and a high Cetane rating in the range of about 60 to 100, and preferably in the range of about 65 to 80. The scrubber tank 33 of the FIGS. 3 and 4 embodiments holds a water bath having a major water constituent (e.g., typically from about 20 to about 90 gal.) and a minor constituent amount (e.g., typically from about 1 to about 2 qts.) of the wetting composition disclosed herein (e.g., a solution of about 0.5% to 2%). Clearly, higher concentrations of the wetting composition in the water bath will perform to attract and hold more DPM over longer operating periods. It should be noted that flushing of the tank (33) and replacement of the aqueous solution periodically (e.g., in the range of about 4 to 6 hours) will be required for optimum performance to achieve “clean air” objectives. This is a low cost, high satisfaction result as compared with the high cost and inefficiency of present prior art systems.

Referring now to FIG. 6, another form of the invention is shown diagrammatically as an exhaust scrubber EE having a scrubber apparatus constructed and arranged to provide a continuous water bath replacement process. In the FIG. 6 embodiment the scrubber tank 133 is relatively small and has a capacity for holding about 4 gallons of the aqueous solution. Similar to the FIG. 3 embodiment, in FIG. 6 the insulated diesel exhaust pipe 135 connects from the engine (12) to the tank 133 at gas intake 134, and an internal extension pipe 137 extends below the tank's water level 138 and has a perforated gas discharge diffuser 139 for dispersing the DPM laden exhaust gas as it is discharged into the water bath WB. The diffuser 139 is shown as discharging exhaust gas radially, outwardly through the water bath, but other gas dispersing means such as the FIGS. 4, 5 embodiment and for a modified and baffle system (144, 145) may be arranged in the water bath. The tank 133 also has a gas discharge outlet 142 located above the water level 138. The feature of the FIG. 6 embodiment is that the aqueous solution of the water bath WB has a continuous feed and is constantly flowing into and through the tank 133 to intimately mix with exhaust gases and remove DPM and carbon monoxide from such exhaust gases.

FIG. 6 shows that the aqueous solution can be prepared by admixing a minor portion of super-wetting agent with a major quantity of water as in a blending tank or mixer 170 constructed to hold a large amount of solution, such as 45 to 90 gal. and from which the flow rate of the water bath solution into tank 133 can be regulated, as at 171. The super-wetting aqueous solution is delivered into the tank through a delivery tube or pipe 172 and discharged through a perforated distributor 173 outwardly in radial directions to maintain level of the water bath WB, in such manner that the exhaust gases as a first medium, are dispersed into or throughout the water bath even as the incoming aqueous solution, as a second medium, is being dispersed therein to achieve the desired intimate turbulence and intermixing whereby the super-wetting agent removes the DPM and cleans the exhaust gases. Thus, the water bath WB of FIG. 6 is not static as the tank 133 has an outlet 174 for regulating the outflow drainage of the aqueous solution from the tank 133 at the predetermined rate so that the solution is constantly flowing into and replacing the water bath content as it is discharged from the tank.

Still referring to FIG. 6, the small volume tank 133 is shown with at least one baffle means 144 extending upwardly from adjacent the floor 146 and at least one baffle means 145 extending down from the top of the tank 133 to enhance circuitous gas flow paths. Through-ports 149 may also be provided in these baffles 144 to increase turbulence and intermixing of the exhaust gases with the aqueous solution. The baffles 145 form vapor seals above the level of the water bath in the tank 133 to force the exhaust gas to pass through the water bath to the exhaust.

It should be noted that the effluent solution from outlet drain 174 can be piped off for remote disposal. However, in most underground mining operations, as in coal mining, water is widely used for different purposes by different equipment, and it is usually discharged as wastewater onto the mining floor where it will be absorbed or from which it may or may not be removed by gravity run-off or through sump action. For instance, water is used in drilling and cutting operations as a coolant for rotary drill bits, long-wall cutting teeth and the like—as well as to remove and flush cuttings away from the drilling or cutting site. Respirable dust is a health threat even as DPM environmental air pollution is a concern addressed by the present invention. Therefore, water is used as a dust suppressant and the disposal methods for effluent mine water from the various diesel systems or other mining equipment are a general concern, but outside the scope of the invention.

Referring to FIGS. 7 and 8, the invention can be carried out in an exhaust scrubber apparatus (EE) having a sealed scrubber tank jacket or housing 233 with an exhaust gas inlet 234 from diesel exhaust pipe 235 at one side and clean gas outlet 242 at the other side. In this embodiment the aqueous solution is discharged in a plurality of adjacent vertical streams (280) as a continuous water bath curtain from the top wall 247 across the width of the scrubber tank 233 to the floor 246 from which the effluent is removed through an outlet drain 274 for disposal. The aqueous solution formed by mixing a super-wetting agent of the invention with water, as in blending tank or mixer 270, is delivered through a flow regulator 271 to a distributor manifold 281 or the like from which it is piped to one or more horizontal perforated pipes 282. The diffuser 239 for spreading out the discharge of exhaust gases in the scrubber tank chamber is constructed and arranged to have a maximum gas discharge area to provide the widest gas dispersion through and intimate contact with the aqueous solution as it passes through the vertical curtain wall of the water bath WB.

The aqueous solutions used in the FIG. 6 and FIG. 7 embodiments will be the same as previously discussed, and only the respective delivery and mixing of exhaust gases therewith is different.

It is now apparent that the objects and advantages of the present invention have been fully met. Changes and modifications of the disclosed forms and combinations of the invention will become apparent to those skilled in the mining field and the providers and operators of diesel equipment in general, and the invention is only to be limited by the scope of the appended claims. 

1. A diesel emissions control system for reducing diesel particulate matter (“dpm”) in diesel engine exhaust to meet environmental control parameters, comprising, a supply of highly paraffinic synthetic diesel fuel for the diesel engine, and apparatus for receiving the emissions output from the diesel engine and being constructed and arranged with filter means through which all exhaust gases must pass before discharge to ambient.
 2. The emissions control system of claim 1, in which said synthetic diesel fuel has a Cetane rating in the range of about 60 to
 100. 3. The emissions control system of claim 2, in which said Cetane rating is in the range of about 65 to
 80. 4. The emissions control system of claim 1, in which said synthetic diesel fuel is characterized by having substantially no sulfur, aromatics or nitrogen content.
 5. The emissions control system of claim 4, in which the synthetic diesel fuel has a sulfur content of less than 1.0%.
 6. The emissions control system of class 4, in which the synthetic diesel fuel has an aromatics content less than 1.0%.
 7. The emissions control system of claim 4, in which the synthetic diesel fuel has a nitrogen content of less than 1.0%.
 8. The emissions control system of claim 1, in which the synthetic diesel fuel is formulated to burn so as to produce a substantially lower “dpm” content in emission gases than in conventional diesel fuels.
 9. The emissions control system of claim 8, in which the reduction in “dpm” content is in the range of 20 to 40%.
 10. The emissions control system of claim 1, in which the synthetic diesel fuel is a linear paraffin-linear olefin fuel formulated to have a Cetane rating over 60 and is characterized by having negligible amounts of sulfur, aromatics and nitrogen.
 11. The emissions control system of claim 1 in which said synthetic diesel fuel comprises a hydrocarbon solvent for the reduction of particulate emissions from diesel engines used in mining and being formulated with a Cetane number above
 60. 12. The emissions control system of claim 1, in which said synthetic diesel fuel comprises a hydrocarbon solvent formulated for reducing the amount of particulate emissions from diesel engines used in metal and non-metal underground mining.
 13. The emissions control system of claim 1, in which said synthetic diesel fuel comprises a hydrocarbon solvent formulated for reducing the amount of particulate emissions from diesel engines used in off-highway, metal and non-metal mining, and coal mining operations.
 14. The emission control system of claim 1, in which said synthetic diesel fuel comprises a hydrocarbon solvent formulated in the boiling range of crude oil and useful for the reduction of particulate emissions from diesel engines used in off-highway applications, and said apparatus being from a class including diesel particulate traps, exhaust catalytic converters, or diesel particulate scrubbers.
 15. A synthetic diesel fuel for low emissions control in diesel engine equipment/machinery, said fuel having a Cetane rating in the range of 60 to 100 and the following properties: (1) a sulfur content of less than 1.0% (2) an aromatics content of less than 1.0% (3) a nitrogen content of less than 1.0%.
 16. The synthetic diesel fuel of claim 15, wherein said fuel is formulated to burn so as to produce a substantially lower “dpm” content in the range of 20% to 40% in emission gases relative to conventional diesel fuels.
 17. The synthetic diesel fuel of claim 15, wherein said fuel is a linear paraffin-linear olefin composition with a minor percentage of branch paraffins and branch olefins.
 18. The synthetic diesel fuel of claim 17, wherein said fuel has less than 5.0% of petroleum-based diesel fuel additive to enhance lubricity.
 19. A method for achieving optimum diesel engine performance and maximum removal of DPM and Co from diesel emission gases, comprising the steps of: formulating a paraffinic-type synthetic diesel fuel characterized by having a high Cetane number over 60 and a negligible amount of sulfur, aromatics and nitrogen content; providing a supply of the fuel for operating the diesel engine to thereby effect a substantial reduction of DPM content in the emissions gasses therefrom; and passing the engine exhaust emissions through discharge filtering means or directly to ambient.
 20. The method according to claim 19, including formulating the synthetic diesel fuel to have a Cetane rating in the range of 60 to
 100. 21. The method according to claim 19, in which the synthetic diesel fuel is formulated to reduce particulate matter in discharged engine emissions by 20% to 40%.
 22. The method of claim 19 in which said discharge filtering means comprises one of a class including particulate traps, particulate scrubbers and catalytic convertors.
 23. The method of claim 19 including the step of using the diesel engine to run equipment/machinery in off-highway, metal/non-metal mining and coal mining operations.
 24. The method according to claim 19, including the further step of pre-filtering the synthetic diesel fuel upstream of the diesel engine to remove non-combustibles therefrom. 